1. Field of the Invention
The present invention relates to an ink-jet recording method by which high-quality color images can be formed at high speed on so-called plain paper such as paper for copying and bond paper.
2. Related Background Art
In recent years, the developments of color displays in personal computers from desktop types to laptop and note types have been advanced. Besides, application softwear for making good use of color's power of expression has been published. Therefore, color recording by printers is the most promising field.
Among various recording processes used in these printers, an ink-jet recording process is a process in which droplets of an ink are formed by any of various ink-ejection systems, and they are applied to a recording material such as paper, converted paper, plastic film or a cloth to conduct recording. The process has advantages that a recording apparatus making use of such a process is silent because a recording head makes no contact with a recording material, printing can be conducted at high speed, and color recording can be achieved with ease.
In the ink-jet recording process, inks used have heretofore been required to have the following properties:
(1) causing no feathering in printed areas on a recording material; PA1 (2) being high in storage stability; and PA1 (3) being high in safety upon their use. PA1 (4) undergoing no color mixing (bleeding) of inks of different colors, which is caused due to unfixing of droplets of the inks when applying them to adjoining portions on a recording material to conduct printing; and PA1 (5) causing no color irregularity, in particular, in color solid-printed areas of the resultant print.
In an ink-jet recording process for conducting color recording, inks are required in addition to the above properties to have the following properties:
However, the inks routinely used have involved a problem that when they are used as inks for color ink-jet recording as they are, bleeding occurs to a great extent, resulting in a failure to form an image. For this reason, exclusive recording materials called coated paper, which are good in ink-absorbing property, have been used to suppress the occurrence of bleeding.
In the case where printing has been conducted on so-called plain paper such as paper for copying and bond paper, there has been a problem that since the printing is conducted while waiting for the ink droplets in the printed area to fix for suppressing the occurrence of bleeding, printing speed becomes very slow. As described above, the inks routinely used have scarcely had selectivity for paper to be used under the circumstances.
In order to improve the resistance to feathering and the fixing property of ink droplets in the printed area on the plain paper as the above-described problems, it has been attempted to use inks the pH of which has been adjusted to strong alkali to conduct recording (for example, Japanese Patent Application Laid-Open No. 56-57862) and to use inks added with a great amount of a surfactant to conduct recording (for example, Japanese Patent Application Laid-Open No. 55-29546).
Even if these inks are used to conduct printing, however, resistance to bleeding is not always sufficiently improved. In the case where bleeding occurs to a relatively small extent, there has also been a problem that the feathering in the printed area as to the item (1) of the above properties required of the inks markedly occurs, resulting in deterioration in image quality. There has not been yet developed under the circumstances any color ink-jet recording ink which can provide high-quality images at high speed even when recording on plain paper.